Text stimulus (graph): A scatter plot titled 'Headline Attention Score and Feed Rank.' X-axis attention score from 1 to 10. Y-axis feed rank position with 1 at top and 20 at bottom, reversed so higher placement is visually higher. Fifteen points show generally higher placement for attention scores 7 to 10. Note: other variables not shown include recency, source size, sponsorship. What is the most important caveat?